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'[PIC]: The Amazing Indestructable PIC!'
2003\04\16@073121 by Philip Pemberton

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Hi all,
I've just finished testing my new PIC programmer (yes, the breadboarded test
model works) and my switchmode PSU just died. Not dead as in no output, but
dead as in 20V straight over the 5V output. Unbelievably, the PIC16F628 that
was connected to the output of said PSU is still working!
It looks like the PIC's ESD protection kicked in and protected it. Well,
that's the best explanation I've got ATM. The 7407 buffer and MAX662 voltage
booster seem to be fine, too. Has anyone ever had a similar experience with
a PIC?

Don't worry, I've learned my lesson... Don't trust the PSU unless it's fitted
with a crowbar circuit... Now where's that 7805...

Later.
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2003\04\16@083136 by Quentin

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Consider yourself lucky. I have blown PICs with less voltage than that.
Forgot to cut a veroboard track between 5V and 12V. Still have a 16F876
with folded legs in my pen tray as a reminder: Check your Voltages
before inserting!
:)

Quentin

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2003\04\16@083235 by D. Jay Newman

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> was connected to the output of said PSU is still working!
> It looks like the PIC's ESD protection kicked in and protected it. Well,
> that's the best explanation I've got ATM. The 7407 buffer and MAX662 voltage
> booster seem to be fine, too. Has anyone ever had a similar experience with
> a PIC?

The only time I've blown a PIC was when I connected the raw battery
supply to an input pin.

This was due mainly to my lack of fine soldering skills. Boy, did that
PIC get *hot*.  :(
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2003\04\16@083239 by Herbert Graf

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> Hi all,
> I've just finished testing my new PIC programmer (yes, the
> breadboarded test
> model works) and my switchmode PSU just died. Not dead as in no
> output, but
> dead as in 20V straight over the 5V output. Unbelievably, the
> PIC16F628 that
> was connected to the output of said PSU is still working!
> It looks like the PIC's ESD protection kicked in and protected it. Well,
> that's the best explanation I've got ATM. The 7407 buffer and
> MAX662 voltage
> booster seem to be fine, too. Has anyone ever had a similar
> experience with
> a PIC?

       While everything might SEEM fine I certainly would no longer trust that
part. PICs are quite tough, but they can also die is ways that make it
REALLY hard to detect they're dead. I had a PIC exposed to "unusual"
circumstances. It seemed to work fine, programmed correctly, ran test
programs correctly. It wasn't until I started using a few peripherals that I
noticed they were dead. If I had been working with that part weeks after the
"incident" I would probably have spent hours trying to debug a problem that
was the fault of a destroyed PIC. Just a heads up. TTYL

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2003\04\16@083508 by Graham North

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We've had a few 'issues' with the ICD2. Only sometimes when you plug it into
the board, the PIC will start drawing loads of current (>400mA), and get
VERY hot (some sort of latch up I expect). Well it happened the other day,
and I got the little hand held IR thermometer we use to find faults on
boards sometimes to see what temperature the PIC was. The thermometer went
over range! >207 deg C!!!!

I turned off the power, let the PIC cool down, powered it up again and it
ran as normal!!!!!

Graham


{Original Message removed}

2003\04\16@090243 by Olin Lathrop
face picon face
> We've had a few 'issues' with the ICD2. Only sometimes when you plug it
> into the board, the PIC will start drawing loads of current (>400mA),
> and get VERY hot (some sort of latch up I expect). Well it happened the
> other day, and I got the little hand held IR thermometer we use to find
> faults on boards sometimes to see what temperature the PIC was. The
> thermometer went over range! >207 deg C!!!!
>
> I turned off the power, let the PIC cool down, powered it up again and
> it ran as normal!!!!!

In that test...  for now...

Ditch it an move on.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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2003\04\16@101136 by Lawrence Lile

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One fun way to test the indestructibility of  a PIC is get it into a bus
fight, where it is trying to drive high and it's opponent is trying to
drive low.  Eventually the port will fry, but all the other ports will
work OK.  The PIC will suck up 50-75 mA just idling along.  In this case,
the breadboard would work fine on my bench power supply, but in the real
application it would get rebootimitis.   The *rest* of the indestructible
PIC survived all this abuse just fine!

I've also seen static zap every chip on the board *except* the pic.

And you can leave one in the UV eraser until the numbers are worn off the
front, and it will still run.

They can also get hot enough to burn your fingers, and still work after
words.


Don't try any of this at home, and especially replace the chips with fresh
ones once these shenanigans are done with.




-- Lawrence Lile





Quentin <KILLspamqscKILLspamspamIPTECH.CO.ZA>
Sent by: pic microcontroller discussion list <RemoveMEPICLISTTakeThisOuTspamMITVMA.MIT.EDU>
04/16/2003 06:40 AM
Please respond to pic microcontroller discussion list


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       Subject:        Re: [PIC]: The Amazing Indestructable PIC!


Consider yourself lucky. I have blown PICs with less voltage than that.
Forgot to cut a veroboard track between 5V and 12V. Still have a 16F876
with folded legs in my pen tray as a reminder: Check your Voltages
before inserting!
:)

Quentin

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2003\04\16@103922 by Philip Pemberton

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In message <NAEALEBPNOHNGKFACEHAOEDBHHAA.mailinglistEraseMEspam.....farcite.net> you wrote:
> I had a PIC exposed to "unusual"
> circumstances. It seemed to work fine, programmed correctly, ran test
> programs correctly. It wasn't until I started using a few peripherals that I
> noticed they were dead.
The bad news: The chip that got blasted is a 20MHz ind-temp 16F268. £11
from Maplins, £5 (iirc) from Farnell. I've got two more, no biggie.
The good news: It was a sample. At least my 16F874s are still in one piece.
Incidentally, if anyone is having trouble with PICs latching up, add a 4k7
pullup to /MCLR and put a 220R between /MCLR and the external reset line.
Programming should still work fine, but the 220R should reduce the current
of any negative-going spikes. I blew a pair of 16F874s before I scoped MCLR.
A negative spike was causing the chip to go into latchup. This was back when
the F87x series was new - 877s were retailing for nearly £12 (while Mchip
ramped up production?) and 874s were £7... Ick...
Even if one of the onchip peripherals turns out to be dead, I can always
put the chip into a random LED flasher or something. Or I could get some
casting resin and turn it into a paperweight...

For those of you who want to see how well hidden the "Don't let MCLR go below
Vss" warning is, have a look at page 149 of the "PIC16F87x Series Datasheet",
Mchip document number DS30292C...

Later.
-- Phil.
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2003\04\16@131413 by Oliver Broad

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Not with a pic but a while back I lost a plugblock 6809 system by dumping
12v on VCC.

Most devices were destroyed but the EEPROM I was using for program storage
survived.

I've a theory that programmable devices are usually (or often or just
sometimes) made so all the chip is capable of running off it's programming
voltage at least if not higher. Result: 12V VPP EPROM parts might withstand
a VCC of 12V, for a while.



{Original Message removed}

2003\04\16@203800 by Tony Nixon

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Philip Pemberton wrote:
>
> Hi all,
> I've just finished testing my new PIC programmer (yes, the breadboarded test
> model works) and my switchmode PSU just died. Not dead as in no output, but
> dead as in 20V straight over the 5V output. Unbelievably, the PIC16F628 that
> was connected to the output of said PSU is still working!
> It looks like the PIC's ESD protection kicked in and protected it. Well,
> that's the best explanation I've got ATM. The 7407 buffer and MAX662 voltage
> booster seem to be fine, too. Has anyone ever had a similar experience with
> a PIC?
>
> Don't worry, I've learned my lesson... Don't trust the PSU unless it's fitted
> with a crowbar circuit... Now where's that 7805...

Yes, I've had an open circuit GND lead on a 7805 which then fed some
overvoltage to a 628 which I'm pretty sure would have glowed in the dark
it got that hot.

Still working in a project too.

It's funny how when you have lots of spares they seem to get through
misshaps like this, but as soon as you only have one left......


regards

Tony

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